4th Announcement of Opportunity (AO-4) for participation in the CHEOPS Guest Observers (GO) Programme

This 4th Announcement of Opportunity (AO-4) marked the start of opportunities in CHEOPS' first extended mission, which ESA's Science Programme Committee (SPC) supported in their meeting on 7 March 2023 (read the full media release here). AO-4 opened on 4 April 2023 and closed on 26 May 2023, soliciting proposals for observations to be carried out as part of the CHEOPS Guest Observers (GO) Programme, with the observation window spanning from 25 September 2023 to 30 September 2024 (inclusive). CHEOPS offers GO observers space-based ultra-high precision photometry for the observation of exoplanet transits, eclipses, occultations, phase-curves, and more. Science cases may range from exomoons, ring structures, stellar activity, and trans-Neptunian objects to other topics beyond the exoplanet field. The timely overlap of several space- and ground-based missions can provide opportunities for synergies with NASA/ESA/CSA JWST, NASA/ESA HST, NASA TESS, ESO ground-based facilities, and more.

Novelties

The CHEOPS AO-4 Call came with several novelties to further enhance community access and the GO experience:

• More targets: only 50 reserved targets, with all the rest being open to the entire community
• More time: up to 30% science observing time dedicated to the GO Programme
• New approach: double-anonymous peer-review of proposals

Milestones

Important Notes

Prospective observers were asked to take note of the following points:

1. Read the Policies and Procedures document carefully before starting any proposal preparation, as it is the definitive document for the AO. It contains details of CHEOPS' science programme, available time for the community, observing strategy and constraints, and required contents of observing proposals. It also lists information about the tools and documents available to support observers in their proposal preparation and submission. Also thoroughly consult the Observers Manual and all relevant documentation on this website.
2. All proposal material and file names must be fully anonymous. This is highlighted in the Policies and Procedures document, and repeated here explicitly to leave no doubts. Failure to comply with this rule will lead to automatic rejection on formal grounds.
3. Consult the Target Checker and Mission Archive. The CHEOPS Science Team kindly made a list of all targets, both reserved and unreserved, as well as their programme information publicly available via these tools. The tool also gives detailed instructions on how to proceed for individual targets.
4. Register to the CHEOPS GO Programme immediately, if you do not already have a user account. Waiting with this step until the deadline might cause you to miss the opportunity.
5. Submit your proposal via the Proposal Handling Tool for Phase I (PHT1). Proposal submission and access to some tools requires the use of a Cosmos ID together with membership of the CHEOPS GO Programme user group.

Please also note that:

• Updates related to this AO Call and its material were published at the bottom of this webpage.
• The CHEOPS team does everything possible to observe and complete awarded programmes. However, it is important to appreciate that an award of observing time does not guarantee that the observations can be conducted, even if a programme is considered to be high-priority science. Due to the nature of the science that CHEOPS addresses, time pressure can be high, unforeseen events can occur, and some observations might not be feasible to schedule.
• CHEOPS is a small mission, with a correspondingly small team to support the GO Programme. Observers are encouraged never to leave proposal preparation to the very last moment, as it may take a couple of days to answer questions.

Key Documentation

• Announcement of Opportunity (AO-4) - invitation letter by the Director of Science
• Policies and Procedures (AO-4)
• Observers Manual (AO-4)
• GTO Programme (AO-4)
• Frequently Asked Questions (FAQ) for AOs
• Is CHEOPS for you?
• In-orbit Updates for Observers

Tools and material

• Registration to the GO Programme - necessary for all following steps
• Phase I Proposal Handling Tool (PHT1) - online tool used for the proposal submission
• Target upload template - a csv-formatted file that may be used for the upload of multiple targets in the PHT1
• Proposal Templates - Word templates for the Science Justification and the Technical Justification and Implementation
• Target Checker - pdf screenshots required for proposal submission
• Reserved Target List (RTL) in csv format - at the AO-4 opening; for quick reference
• Mission Archive - to consult previous observations and public data
• Exposure Time Calculator (ETC) - including online help; pdf export of results required for proposal submission
• Scheduling Feasibility Checker (SFC) - including installation and user guidelines
• Pycheops' function make_xml_files - a community-developed tool to generate XML files for input to the SFC, based on a data table for multiple observing requests provided by the user. Users may use this tool at their own risk, with caveats and warnings detailed in the documentation.

Additional references   

• CHEOPS mission paper - Benz et al., 2021
• CHEOPS visibility maps - a collection of all annual accumulated maps, monthly maps, and ascii files, as well as an updated README file
• CHEOPS point spread function (PSF) - in orbit measurements; also available directly from the CHEOPS archive as REF_APP_WhitePSF
• CHEOPS bandpass - including the numerical data, i.e. QE curve and optical throughput, required to calculate it
• CHEOPS Data webpage - details of selected CHEOPS data taken during IOC that is already public, simulated data and reference data
• CHEOPS Data Products Definition Document (DPDD) - detailed description of the content of CHEOPS data products and associated files
• Simulated CHEOPS data - various data products and ancillary files, reports, and documentation (pre-launch, included for information)

Updates

• Note the special case of Alpha Cen, including Alpha Cen A and Alpha Cen B: the system was on the RTL, but due to its high proper motion and orbital motion, the Target Checker did not resolve its RTL coordinates if queried by name. Alpha Cen’s RTL coordinates were given in the RTL csv file and had to be used for any Target Checker queries for this system.
• Additional examples to help users make their proposals dual-anonymous were added to the FAQ pages.